The subject matter disclosed herein relates generally to x-ray tubes used in imaging systems and more particularly, to x-ray tubes generating two different energy levels of x-rays.
Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward a subject or object, such as a patient or a piece of luggage. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the object. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately produces an image.
Material decomposition involves measuring an x-ray absorption characteristic of a material for two different energy levels of x-rays. Dual energy scanning can be used to obtain diagnostic CT images that enhance contrast separation within the image by utilizing two scans at different chromatic energy states. A number of techniques are known to achieve dual energy scanning, including acquiring two back-to-back scans sequentially in time where the scans require two rotations around the object in which the tube operates at, for instance, 80 kVp and 140 kVp potentials. Alternatively, two-tube-two-detector architecture enables acquiring two scans simultaneously, but with a difference in phase. Taking separate scans several seconds apart from one another or acquisitions that are different in phase result in mis-registrations between datasets caused by patient motion (both external patient motion and internal organ motion). Additionally, a dual-tube, dual-detector system also results in poor registration of data acquired at two energies and introduces artifacts due to the difference in acquisition time and phases respectively.